electronics Article D-Band Frequency Tripler Module Using Anti-Parallel Diode Pair and Waveguide Transitions Jihoon Doo, Jongyoun Kim and Jinho Jeong * Department of Electronic Engineering, Sogang University, Seoul 04107, Korea; [email protected] (J.D.); [email protected] (J.K.) * Correspondence: [email protected]; Tel.: +82-2-705-8934 Received: 1 July 2020; Accepted: 24 July 2020; Published: 27 July 2020 Abstract: In this paper, D-band (110–170 GHz) frequency tripler module is presented using anti-parallel GaAs Schottky diode pair and waveguide-to-microstrip transitions. The anti-parallel diode pair is used as a nonlinear device generating harmonic components for Q-band input signal (33–50 GHz). The diode is zero-biased to eliminate the bias circuits and thus minimize the number of circuit components for low-cost hybrid fabrication. The anti-parallel connection of two identical diodes effectively suppresses DC and even harmonics in the output. Furthermore, the first and second harmonics of Q-band input signal are cut off by D-band rectangular waveguide. Input and output impedance matching networks are designed based on the optimum impedances determined by harmonic source- and load-pull simulations using the developed nonlinear diode model. Waveguide-to-microstrip transitions at Q- and D-bands are also designed using E-plane probe to package the frequency tripler in the waveguide module. The compensation circuit is added to reduce the impedance mismatches by bond-wires connecting two separate substrates. The fabricated frequency tripler module produces a maximum output power of 5.4 dBm at 123 GHz under input power of 20.5 dBm. A 3 dB bandwidth is as wide as 22.5% from 118.5 to 148.5 GHz at the input power of 15.0 dBm. This result corresponds to the excellent bandwidth performance with a conversion gain comparable to the previously reported frequency tripler operating at D-band. Keywords: diode; frequency multiplier; millimeter-wave; transition; tripler; waveguide 1. Introduction Millimeter-wave frequency band ranging from 30 to 300 GHz finds a lot of commercial and military applications such as high-speed wireless communications and high-resolution radar sensors, since it allows for wide bandwidth and small wavelength (10–1 mm). It is essential to develop the semiconductor-based devices or circuits generating high purity and high power signals for millimeter-wave communication and radar applications. Fundamental oscillators operating at millimeter-wave above 100 GHz have been introduced in the form of integrated circuits (ICs) using silicon CMOS or compound semiconductor technologies [1–3]. However, the fundamental oscillator ICs exhibit very limited output power and phase noise performance at millimeter-wave frequencies. This is caused by the transistors of which output powers are inversely proportional to the frequency. Another approach to generating millimeter-wave signals is to design frequency multipliers which extract the wanted harmonic frequency component generated by the non-linear devices for high-purity and low-frequency input signal, while rejecting the other unwanted harmonic frequency components [4]. Frequency multipliers can be designed using nonlinear semiconductor devices such as diodes or transistors. In millimeter-wave frequency above 100 GHz, GaAs Schottky diodes are commonly used for frequency multipliers, since they exhibit very high cut-off frequency and high output powers. It has another advantage in that it can be fabricated in the form of low-cost hybrid circuits [5]. In the Electronics 2020, 9, 1201; doi:10.3390/electronics9081201 www.mdpi.com/journal/electronics Electronics 2020, 9, x FOR PEER REVIEW 2 of 11 It has another advantage in that it can be fabricated in the form of low‐cost hybrid circuits [5]. In the Electronics 2020, 9, 1201 2 of 11 frequency multipliers, it is important to filter out the spurious signals generated by the nonlinear devices, while amplifying the wanted harmonic component. In the diode‐based frequency multipliers, thefrequency unwanted multipliers, harmonic it spurious is important can be to filtereffectively out the suppressed spurious signalsusing the generated special connection by the nonlinear of the diodes.devices, The while balanced amplifying type the multipliers wanted harmonic cancel out component. odd‐order In harmonic the diode-based frequency frequency components multipliers, at the outputthe unwanted by applying harmonic input spurious signals with can 180° be eff outectively of phase suppressed to the diodes using [6–9]. the special On the connection contrast, DC of and the evendiodes.‐order The harmonic balanced components type multipliers are cancelled cancel out out odd-order at the output harmonic of anti frequency‐parallel diode components pair which at the is thusoutput widely by applying applied inputfor the signals design with of millimeter 180◦ out of‐wave phase frequency to the diodes triplers [6– [10,11].9]. On theIn order contrast, to reject DC and the fundamentaleven-order harmonic component, components waveguide are cancelledor microstrip out at filters the output can be of placed anti-parallel at the diode input pair of the which anti is‐ parallelthus widely diode applied pair [12–14]. for the designPower ofcombiners millimeter-wave in the waveguide frequency triplersare often [10 employed,11]. In order to increase to reject the outputfundamental power component, at 3rd harmonic waveguide component or microstrip [15,16]. filters can be placed at the input of the anti-parallel diodeIn pair this [ 12work,–14]. we Power design combiners a D‐band in (110–170 the waveguide GHz) frequency are often tripler employed using to anti increase‐parallel the outputpair of powercommercial at 3rd GaAs harmonic Schottky component diodes. [15 We,16 ].develop the nonlinear diode model using the datasheet providedIn this by work, the wevendor design and a D-band electromagnetic (110–170 GHz)simulations. frequency Harmonic tripler using source anti-parallel‐ and load pair‐pull of simulationscommercial are GaAs performed Schottky using diodes. the develop We develop nonlinear the diode nonlinear model diode to find model the optimum using the impedances datasheet providedfor high conversion by the vendor gain. and Input electromagnetic and output matching simulations. circuits Harmonic are then source- designed and load-pull to produce simulations high 3rd harmonicare performed power using while the rejecting develop the nonlinear spurious diode signals. model The to frequency find the optimum tripler is impedances mounted inside for high the waveguideconversion gain.by designing Input and the output waveguide matching‐to‐microstrip circuits are transitions then designed at the to Q‐ produceand D‐band high using 3rd harmonic E‐plane powerprobes. while The compensation rejecting the spuriouscircuit is also signals. designed The frequency to minimize tripler impedance is mounted mismatches inside the caused waveguide by the bondby designing‐wires connecting the waveguide-to-microstrip the circuits in two separate transitions substrates at the with Q- and different D-band width using for E-plane Q‐ and D probes.‐band Thetransitions. compensation In Section circuit 2, the is also design designed of a D‐ toband minimize frequency impedance tripler mismatchesmodule is presented caused by including the bond-wires diode model,connecting impedance the circuits matching in two separate of frequency substrates tripler, with di ffwaveguideerent width fortransitions, Q- and D-band and transitions.bond‐wire compensationIn Section2, the circuit. design Measurement of a D-band frequencyresults are tripler given modulein Section is presented 3, together including with the diode performance model, comparisonimpedance matching with other of works. frequency tripler, waveguide transitions, and bond-wire compensation circuit. Measurement results are given in Section3, together with the performance comparison with other works. 2. Design of D‐Band Frequency Tripler Module 2. Design of D-Band Frequency Tripler Module 2.1. GaAs Schottky Diode 2.1. GaAs Schottky Diode We select GaAs Schottky diode (5VA30–13 by ACST) for the design of D‐band frequency tripler in whichWe select three GaAs anodes Schottky are connected diode (5VA30–13 in series by as ACST) illustrated for the in design Figure of 1 D-band [17]. Figure frequency 2a shows tripler the in which three anodes are connected in series as illustrated in Figure1[ 17]. Figure2a shows the equivalent equivalent circuit model of a single anode consisting of current source iD, junction capacitance Cj, circuit model of a single anode consisting of current source iD, junction capacitance Cj, junction leakage junction leakage conductance Gleak, and series resistance RS. The iD and Cj are dependent on diode conductance Gleak, and series resistance RS. The iD and Cj are dependent on diode voltage vD as given voltage vD as given in (1) and (2), where IS and n are a saturation current and ideality factor, in (1) and (2), where IS and n are a saturation current and ideality factor, respectively [6]. In (2), Cj0 and respectively [6]. In (2), Cj0 and Vj represent zero‐bias junction capacitance and built‐in voltage, V represent zero-bias junction capacitance and built-in voltage, respectively. The parameters of the respectively.j The parameters of the equivalent circuit are extracted using the datasheet and equivalent circuit are extracted using the datasheet and measurement data provided by the vendor. measurement data provided by the vendor. Figure 1. GaAsGaAs Schottky diode (three (three-anodes‐anodes in series). vD vD nVT iD = IS (enVT 1) (1)(1) iD = IS (e ‐ −1) r vD Cj = Cj0/ 1vD (2) Cj = Cj0/1‐− V j (2) Vj Figure2b shows the equivalent circuit of the three-anode diode including the parasitic series inductance LS and parallel capacitance Cp in each anode. The pad capacitance on both ends is Electronics 2020, 9, x FOR PEER REVIEW 3 of 11 Electronics 2020, 9, 1201 3 of 11 Figure 2b shows the equivalent circuit of the three‐anode diode including the parasitic series inductance LS and parallel capacitance Cp in each anode. The pad capacitance on both ends is represented by Cg [18].